Assembly for feeding in HF current for tubular cathodes

Abstract

An arrangement is provided for feeding in HF current for rotatable tubular cathodes in a vacuum chamber of a plasma coating system as well as a high frequency current source. Located inside the tubular cathode is a magnet arrangement that extends along said tubular cathode for generating a magnetic field. The arrangement enables a low loss infeed of HF current, so that a particularly homogeneous sputter removal from the tubular cathode is guaranteed. The HF current source is coupled to the tubular cathode inside the vacuum chamber by a capacitive infeed of HF current in the form of a coupling capacitor. The coupling capacitor includes a part of the surface of the tubular cathode and a metal plate or metal film that surrounds the tubular cathode, at least partially, at a specified distance.

The invention claimed is: 
     
       1. An arrangement for feeding in HF current for a rotatable tubular cathode serving as a sputtering target in a vacuum chamber of a plasma coating system, the rotatable tubular target comprising a support tube supporting a target shell, the target shell comprising target material to be removed during sputtering and deposited on a substrate, in combination with a high frequency current source and a matching network and, located inside said tubular cathode, a stationary magnet arrangement that extends along said tubular cathode, wherein the HF current source is coupled via the matching network to the tubular cathode inside the vacuum chamber by a coupling capacitor, the coupling capacitor consisting of a part of a surface of the tubular cathode and a metal plate or metal film surrounding approximately half of the rotatable tubular cathode at a specified distance from said surface, wherein the metal plate or metal film extends substantially over an entire free length of the tubular cathode inside the vacuum chamber, and wherein the metal plate or metal film is located diametrically opposite the stationary magnet arrangement so as not to impede sputtering of the target material of the target shell, and wherein the coupling capacitor serves as a capacitor of the matching network or the coupling capacitor replaces a capacitor of the matching network at the same time as serving as a capacitive infeed of HF current to the rotatable tubular cathode, and wherein the specified distance is readjusted during sputtering as a function of decreasing diameter of the tubular cathode due to removal of target material from the target shell. 
     
     
       2. Arrangement, as claimed in  claim 1 , wherein the metal plate or metal film has a semi-cylinder shape that is arranged at a uniform specified distance from the tubular cathode. 
     
     
       3. Arrangement, as claimed in  claim 1 , wherein the specified distance comprises approximately 2 mm. 
     
     
       4. Arrangement, as claimed in  claim 1 , wherein the metal plate or metal film is provided with a dark field shielding. 
     
     
       5. Arrangement, as claimed in  claim 4 , wherein an insulation is arranged between the metal plate or metal film and the shielding, the insulation reducing reactive current while simultaneously ensuring a uniform specified distance over an entire length and width of the coupling capacitor. 
     
     
       6. Arrangement, as claimed in  claim 4 , wherein the shielding is connected to ground. 
     
     
       7. An arrangement for feeding in HF current for a rotatable tubular cathode serving as a sputtering target in a vacuum chamber of a plasma coating system, the rotatable tubular cathode comprising a support tube supporting a target shell, the target shell comprising target material to be removed during sputtering and deposited on a substrate, in combination with a high frequency current source and a matching network and, located inside said tubular cathode, a stationary magnet arrangement that extends along said tubular cathode, wherein the HF current source is coupled via the matching network to the tubular cathode inside the vacuum chamber by a coupling capacitor, the coupling capacitor comprising a part of a surface of the tubular cathode and a metal plate or metal film that surrounds the tubular cathode at least partially at a specified distance from said surface, wherein the metal plate or metal film is provided only at both ends of the tubular cathode so as to not impede sputtering of the target material of the target shell, and wherein the coupling capacitor serves as a capacitor of the matching network or the coupling capacitor replaces a capacitor of the matching network at the same time as serving as a capacitive infeed of the HF current to the rotatable tubular cathode, and wherein the specified distance is readjusted during sputtering as a function of decreasing diameter of the tubular cathode due to removal of target material from the target shell. 
     
     
       8. Arrangement, as claimed in  claim 7 , wherein the metal plate or metal film provided only at both ends of the tubular cathode comprises sleeves fully surrounding the ends of the tubular cathode. 
     
     
       9. Arrangement, as claimed in  claim 1 , wherein the coupling capacitor is a component of the matching network of the HF power supply, the matching network further comprising a capacitor and a coil in series with the coupling capacitor, and a parallel capacitor. 
     
     
       10. Arrangement, as claimed in  claim 5 , wherein the insulation comprises a synthetic plastic material sandwiched between the metal plate or metal film and the dark field shielding. 
     
     
       11. Arrangement, as claimed in  claim 7 , wherein the metal plate or metal film has a semi-cylinder shape and is surrounded on a rear side facing away from the tubular cathode by dark field shielding, with insulation sandwiched between the rear side of the metal plate or metal film and the shielding reducing a reactive current.